Sheet feeding apparatus and paper separation device thereof

ABSTRACT

A sheet feeding apparatus includes an input tray, a paper picking device, and a paper separation device. The input tray is for placing a plurality of papers. The paper picking device is for performing a paper picking operation on the papers. The paper separation device, including a paper separation surface contacting with the papers placed on the paper tray, is for applying a paper separation force on each of the papers as fed in. When the paper picking device performs the paper picking operation on each of the papers, the paper separation forces applied on the papers are decreased as their paper separation paths are increased.

This application claims the benefit of Taiwan application Serial No. 94122429, filed on Jul. 1, 2005, the subject matter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to a sheet feeding apparatus and paper separation device thereof, and more particularly to a sheet feeding apparatus, which can apply suitable paper separation forces on the fed-in papers according to the amount of the papers, and paper separation device thereof.

2. Description of the Related Art

Generally, in a printer, papers are fed in for print via a sheet feeding mechanism. In order to meet the requirements for papers having various feeding features, a paper separation device is usually configured in the sheet feeding mechanism to separate the papers, and the papers can thus be fed into the printer piece by piece.

FIG. 1A is a lateral view of a conventional sheet feeding mechanism in a printer. Referring to FIG. 1A, the sheet feeding mechanism 100 includes an input tray 110, a pick roller 120 and a buckler 130. The input tray 110 is for placing a pile of to-be-printed papers 111. The buckler 130 has one end connected to the input tray 110 and supports the pile of to-be-printed papers 111. The pick roller 120 applies a pick force Fc on the papers 111 in a rolling friction way to slide the front edge A of the uppermost paper 111 along the surface of the buckler 130 and then feed the papers 111 into a print module 140 of the printer.

FIG. 1B is a schematic enlarged view of the sheet feeding mechanism 100 in FIG. 1A. Referring to FIG. 1B, the surface of the buckler 130 has generally a saw structure 132 for applying a paper separation force Fr on the papers 111 to be fed in to achieve the effect of paper separation. The saw structure 132 has several saw strips 134 having the same shape and size. Through the saw strips 134, the buckler 130 can apply suitable paper separation forces Fr on the papers 111 to prevent a paper gliding issue as the above-mentioned pick roller 120 (not shown in the figure) applies a pick force Fc to slide the papers 111.

As described above, when the amount of papers 111 decreases, and the uppermost paper 111 is moved from the point G to the point H as shown in FIG. 1C, the center of the pick roller 120 is moved from the point O′ to the point O″. Under the situation of equal driving torque, the driving force F vertical to the central line I of the roller 120 should be a constant. The normal force Fn′ applied by the roller 120 located at the point O′ is equal to F·cos(a′) while the normal force Fn″ applied by the roller 120 located at the point O″ is equal to F·cos(a″). However, since the angle a″ is larger than the angle a′, the normal force Fn″ is smaller than Fn′. Therefore, the pick force Fc″ (=Fn″·μ) is also smaller than Fc′(=Fn′·μ). When the amount of papers 111 decreases, due to swing angle variation of the roller 120, the pick force Fc for sliding the papers 111 is reduced and thus a miss-feed issue that no paper is picked up to slide or a motor miss-step issue that the papers 111 are fed in by a delay of one or two seconds is generated. Besides, as shown in FIG. 1A, when the amount of to-be-printed papers 111 increases, owing that paper separation path measured from the front edge A of the paper 111 to the end B of the buckler 130 near the print module 140 is decreased, a paper gliding issue can be easily generated due to mechanic vibration or static electricity. Moreover, because the pick force Fc applied on the papers 111 by the roller 120 is increased, a multi-feed issue can be easily generated to slide multiple papers at a time.

In order to provide enough forces for sliding the papers and prevent the paper gliding issue, a paper separator of a printer is disclosed in the U.S. Pat. No. 6,536,757 as shown in FIG. 2A. The paper separator 200 includes a dam 201, and the dam 201 has a friction bracket 210 and a jack buckler 220. The friction bracket 210, having function like the buckler 130 mentioned above, uses a saw structure 212 to generate the required paper separation effect. A guide projection 222, a first saw structure 224, and a second saw structure 226 is configured in order on the jack buckler 220. The guide projection 222 is for guiding the to-be-printed papers 211 as sliding. The to-be-printed papers 211 are connected to both the surfaces of the saw structure 212 and the jack buckler 220.

As shown in FIG. 2B, each saw 225 in the first saw structures 224 has a sliding side 225 a and a threshold side 225 b and each threshold side 225 b has an inclined angle α against the vertical line K of the jack buckler 220. Each saw 227 in the second saw structure 226 has a sliding side 227 a and a threshold side 227 b, and each threshold side 227 b has an inclined angle β against the line K, wherein the angle α is larger than the angle β. When the front edge of the paper 211 is fed in along the paper feeding direction L, the paper gilding is generated as the paper 211 is being fed in through the guide projection 222 due to mechanic vibration. At the time, no matter the front edge of the paper 211 glides between the threshold side 225 b and the sliding side 225 a of two adjacent saws 225, or between the threshold side 227 b and the sliding side 227 a of two adjacent saws 227, the threshold side 225 b or 227 b applies an extra resisting force on the paper 211 to prevent the paper 211 from gliding continuously.

However, the above-mentioned paper separator 200 has the following disadvantages:

1. Owing that the paper separator 200 uses the saw structures 212, 224, 226 on the friction projection 210 and the jack buckler 222 to generate paper separation forces, the resisting force for the fed-in papers 211 is relatively increased and the motor miss-step risk is thus enhanced.

2. Owing that the papers 211 stay at one side of the guide projection 222 at the beginning of paper feeding, the path for paper feeding is increased, thereby enlarging the mechanism size and mechanical resistance force in feeding papers.

3. When the amount of papers decreases or papers of higher rigidity are used for print, the paper separation forces are not reduced accordingly. Therefore, the above-mentioned miss-feed and motor miss-step issues cannot be prevented.

4. Except for the friction projection 210 served as a paper separation device, the paper separator 200 uses an extra jack buckler 220 to prevent the paper gliding issue, which increases, however, the mechanism cost.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a sheet feeding apparatus and paper separation device thereof. By a suitable design of the surface structure of the paper separation device, the paper separation forces applied on the fed-in papers by the surface of the paper separation device are decreased as the paper separation paths of the papers are increased. Therefore, the paper gliding and the multi-feed issues easily generated in a large paper amount and the miss-feed and motor miss-step issues easily generated in a small paper amount can be prevented.

The invention achieves the above-identified object by providing a paper separation device used in a sheet feeding apparatus. The sheet feeding apparatus includes an input tray for placing a number of papers The paper separation device includes a paper separation surface. The paper separation surface, contacting with the papers placed on the input tray, is for applying a paper separation force on each of the papers as fed in. The paper separation forces applied on the fed-in papers are decreased as their paper separation paths are increased.

The invention achieves the above-identified object by providing a sheet feeding apparatus including an input tray, a paper picking device, and a paper separation device. The input tray is for placing a plurality of papers. The paper picking device is for performing a paper picking operation on the papers. The paper separation device, including a paper separation surface contacting with the papers placed on the paper tray, is for applying a paper separation force on each of the papers as fed in. When the paper picking device performs the paper picking operation on each of the papers, the paper separation forces applied on the papers are decreased as their paper separation paths are increased.

Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a lateral view of a conventional sheet feeding mechanism in a printer.

FIG. 1B is a schematic enlarged view of the sheet feeding mechanism in FIG. 1A.

FIG. 1C is a schematic diagram showing that the pick force applied by the pick roller decreases as the amount of papers is reduced due to swing angle variation of the roller.

FIG. 2A is a solid view of a paper separator of a printer disclosed in U.S. Pat. No. 6,536,757.

FIG. 2B is a lateral view of the jack buckler in FIG. 2A.

FIG. 3 is a lateral view of a sheet feeding apparatus according to a preferred embodiment of the invention.

FIG. 4A is a partially lateral view of the paper separation device in FIG. 3.

FIG. 4B is a schematic diagram showing the paper separation device in FIG. 4A provides the paper separation force as the amount of papers is large.

FIG. 4C is a schematic diagram showing the paper separation device in FIG. 4A provides the paper separation force as the amount of papers is small.

FIG. 5A, another partially lateral view of the paper separation device in FIG. 3.

FIG. 5B is a schematic diagram showing the paper separation device in FIG. 5A provides the paper separation force as the amount of papers is large.

FIG. 5C is a schematic diagram showing the paper separation device in FIG. 5A provides the paper separation force as the amount of papers is small.

FIG. 6 is a partially lateral view of the third structure of the paper separation device in FIG. 3.

FIG. 7 is a partially lateral view of the fourth structure of the paper separation device in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 3, a lateral view of a sheet feeding apparatus according to a preferred embodiment of the invention is shown. The sheet feeding apparatus 300, used in an electronic device, such as a printer, a fax machine, or a multi-function printer, includes an input tray 310, a pick roller 320, and a paper separation device 330. The input tray is for placing a pile of to-be-printed papers 311. The pick roller 320 applies a pick force Fc on the papers 311 in a rolling friction way to perform a paper picking operation. The paper separation device includes a paper separation surface 332, contacting with the papers 311 placed on the input tray 310, for applying paper separation forces Fr on the papers 311 as the papers 311 are picked up by the pick roller 320 to slide in. In the following description, two examples are taken to illustrate how the paper separation device 330 of the sheet feeding apparatus 300 in the invention prevents the prior art disadvantages.

EXAMPLE ONE

Referring to FIG. 4A, a partially lateral view of the paper separation device 330 in FIG. 3 is shown. The paper separation surface 332 includes n saw strips 333 arranged in parallel and adjacent to each other along the paper feeding direction Lp with all the saw strips 333 having the same height h. Each saw strip 333 has a sliding side 333 a facing to the paper feeding direction Lp and a threshold side 333 b facing against the paper feeding direction Lp. The threshold sides 333 b have inclined angles a (a1˜an) against the line K vertical to the surface of the paper separation surface 332, wherein the inclined angles a (a1˜an) are decreased along the paper feeding direction Lp, that is, a1<a2< . . . <an. The sliding sides 333 a of the saw strips 333 are parallel to each other. The number n of the saw strips 333 is exemplified to be 10 in FIG. 4A.

As shown in FIG. 4B, when the amount of papers 311 is large and the relative paper separation path for each paper is small, such as 100 pieces of papers for print at a time, the above-mentioned pick roller 320 (not shown in the figure) has a larger pick force Fc1 than that force provided in a normal paper amount due to swing angle variation of the roller 320. However, the uppermost paper 311 a in the pile of papers 311 is located at one end M of the paper separation surface 332 having a smaller angle a. Because the paper separation force Fr1 applied on the paper 311 a by the saw strips 333 of the paper separation surface 332 is larger than that force provided in a normal paper amount, the above-mentioned paper gliding and multi-feed issues can be prevented. Furthermore, when the amount of papers 311 is large, the papers 311 are usually of lower rigidity, such as A4 plain papers. Therefore, the issue can be prevented that papers 311 are not fed in due to resistance of the saw strips 333.

Besides, as shown in FIG. 4C, when the amount of papers 311 is small and the paper separation path for each paper is large, the pick force Fc2 applies on the papers 311 by the above-mentioned pick roller 320 (not shown in the figure) is smaller than that force provided in a normal paper amount. However, at the time, the uppermost paper 311 a in the pile of the papers 311 is located at one end N of the paper separation surface 332 having a larger angle a. Owing that the paper separation force Fr2 applied on the paper 311 a by the saw strips 333 of the paper separation surface 332 is smaller than that paper separation force provided in a normal paper amount, the papers 311 are more easily separated and fed in piece by piece. Especially when the papers 311 of higher rigidity, such as photo papers, are used for print, the miss-feed and motor miss-step issues mentioned above can be prevented.

It is noted that although it is exemplified that the sliding sides 333 a of the saw strips 333 are parallel to each other and the inclined angles a of the threshold sides 333 b are decreased along the paper feeding direction in the first example as shown in FIG. 4A, in the paper separation surface 332 of the invention, the sliding sides 333 a of the saw strips 333 can also be not in parallel and the height h of the saw strips 333 can also be different. As long as the angles between two adjacent saw strips 333 (the angles between the adjacent threshold sides 333 b and the sliding sides 333 a) are decreased along the paper feeding direction, all these alternatives can still prevent the paper gliding and multi-feed issues happened in a large paper amount and small paper separation path as well as the miss-feed and motor miss-step issues happened in a small paper amount and large paper separation path.

EXAMPLE TWO

Referring to FIG. 5A, another partially lateral view of the paper separation device 330 in FIG. 3 is shown. The paper separation surface 332 includes m saw strips 533 arranged in parallel and adjacent to each other along the paper feeding direction Lp with the saw strips 533 having the same height h. Each saw strip has a sliding side 533 a facing to the paper feeding direction Lp and a threshold side 533 b facing against the paper feeding direction Lp. The threshold sides 533 b of the saw strips 533 are in parallel. The vertical height H (H1˜Hm) from the bottom C to the top D of the threshold side 533 b, that is, the depth of the gaps 535 of the saw strips 533, is increased along the paper feeding direction, i.e. H1>H2> . . . >Hm. The number m of the saw strips 533 is exemplified to be 10 in FIG. 5A.

As shown in FIG. 5B, when the amount of papers 311 is large and the paper separation path for each paper is small, the pick force Fc3 is larger than that in a normal paper amount. However, the uppermost paper 311 a in the pile of the papers 311 is located at one end P of the paper separation surface 532 where the gap depth H of the saw strips 533 is larger. Therefore, the paper separation force Fr3 applied on the paper 311 a by the saw strips 533 of the paper separation surface 532 is larger than that force in a normal paper amount, thereby preventing the paper gliding and multi-feed issues. As shown in FIG. 5C, when the amount of papers 311 is small and the paper separation path for each paper is large, the pick force Fc4 is smaller than that in a normal paper amount. However, the uppermost paper 311 a in the pile of papers 311 is located at one end Q of the paper separation surface 532 where the gap depth H of the saw strips 533 is smaller. Therefore, the paper separation force Fr4 applied on the paper 311 a by the saws 533 of the paper separation surface 532 is smaller than that force provided in a normal paper amount, thereby preventing the miss-feed and motor miss-step issues.

It is noted that although it is exemplified in the second example that the threshold sides 533 b of the saw strips 533 are in parallel and the depth H of the gaps between two adjacent saw strips 533 is increased along the paper feeding direction Lp, in the paper separation surface 532 of the invention, the threshold sides 533 b of the saw strips 533 can also be not in parallel, and the height h of the saw strips 333 can also be different. As long as the angles between two adjacent saw strips 533 (the angles between the adjacent threshold sides 533 b and the sliding sides 533 a) are decreased along the paper feeding direction, and the depth H of the gaps between two adjacent saw strips 533 is increased along the paper feeding direction Lp, all the alternatives can still prevent the paper gliding and multi-feed issues happened in a large paper amount and small paper separation path as well as the miss-feed and motor miss-step issues happened in a small paper amount and large paper separation path.

As described above, although it is exemplified that the inclined angles a are decreased or the depth of the saw gaps is increased along the paper feeding direction Lp in the invention, the invention is not limited thereto. In the paper separation device, the saw angles of the paper separation surface can also be increased along the paper feeding direction or the depth of the saw gaps can also be decreased along the paper feeding direction. As long as the paper separation forces are decreased as the paper separation paths of the fed-in papers are enlarged, the multi-feed and miss-feed issues can be prevented. Therefore, all these are not apart from the scope of the invention.

According to the two examples mentioned above, although it is exemplified that the saw strips (333 or 533) have the same height h and different saw angles a or gap depth H, the paper separation surface 332 of the invention can also have saw strips of different height or have certain saw strips of the same height and the rest of different height. As long as the saw height and accordingly the saw gap depth is increased along the paper feeding direction while the angles between two adjacent saws are the same or are decreased along the paper feeding direction, the above-mentioned paper separation issue can be prevented. The saw height, saw angles, and saw gap depth of the paper separation surface 332 can be even designed suitably so that the paper separation force applied on the papers by the paper separation surface can be decreased as the paper amount is reduced, thereby achieving the purpose of preventing the above-mentioned paper separation issues.

In addition, although the paper separation surface 332 having saw strips 333 or 533 is taken as an example in the invention, the paper separation surface 332 of the paper separation device 330 in the invention can also includes a number of circular protrusions 633 or some saw strips (333 or 533) and some circular protrusions 633 having the same height h as shown in FIG. 6. The circular protrusions 633 are arranged regularly along the paper feeding direction Lp and the size of the gaps between two adjacent circular protrusions 633 (i.e. the distance dl between two adjacent circular protrusions 633) is decreased along the paper feeding direction Lp. Or the paper separation surface 332 of the paper separation device 330 in the invention can also include a number of circular protrusions 733 having the same height h and equal interval d2 as shown in FIG. 7. The circular protrusions 733 are arranged regularly along the paper feeding direction Lp, and the depth s of the gaps between two adjacent circular protrusions is increased along the paper feeding direction Lp.

Although the paper separation surface 332 having saw strips 333, 533, or circular protrusions 633, 733 is taken as an example in the invention, the paper separation surface 332 of the paper separation device 330 in the invention can also include other protrusions of a regular shape or an irregular shape. The paper separation surface can also even be surface-processed suitably to provide the paper separation force required for the papers in a surface friction way. As long as the paper separation forces applied on the fed-in papers are decreased as their paper separation paths are increased, the papers gliding and multi-feed issues easily happened in a large paper amount or the miss-feed and motor miss-step issues easily happened in a small paper amount can be prevented. Therefore, all these will not depart from the scope of the invention.

The sheet feeding apparatus and paper separation device thereof disclosed by the above-mentioned embodiment of the invention has the following advantages:

1. The invention can prevent the paper gliding and motor miss-step issues by a direct surface structure design of the paper separation device without using extra auxiliary devices.

2. By decreasing the paper separation forces applied on the papers as their paper separation paths are increased, the invention can prevent the paper gliding and multi-feed issues easily happened in a large paper amount and the miss-feed and motor miss-step issues easily happened in a small paper amount.

3. By using the paper separation surface to provide a smaller paper separation force as the paper has a larger paper separation path, the invention can prevent the motor miss-step issue or the miss-feed issue happened as feeding the papers of higher rigidity.

While the invention has been described by-way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures. 

1. A paper separation device, used in a sheet feeding apparatus, the sheet feeding apparatus comprising an input tray for placing a plurality of papers, the paper separation device comprising: a paper separation surface, contacting with the papers placed on the input tray, for applying a paper separation force on each of the papers as fed in; wherein the paper separation forces applied on the fed-in papers are decreased as their paper separation paths are increased.
 2. The paper separation device according to claim 1, wherein the paper separation surface comprises a plurality of protrusions arranged along a paper feeding direction for providing the paper separation force.
 3. The paper separation device according to claim 2, wherein the protrusions of a regular or an irregular shape have the same or different height.
 4. The paper separation device according to claim 2, wherein the protrusions are a plurality of saw strips.
 5. The paper separation device according to claim 4, wherein the size of saw gaps between the tops of two adjacent saws is decreased along the paper feeding direction.
 6. The paper separation device according to claim 5, wherein each of the saw strip has a first surface facing to the paper feeding direction and a second surface facing against the paper feeding direction, the first surfaces are arranged in parallel, and the second surfaces have decreased inclined angles against a vertical line of the paper separation surface along the paper feeding direction.
 7. The paper separation device according to claim 4, wherein the saw strips have gap depth increased along the paper feeding direction.
 8. The paper separation device according to claim 7, wherein each of the saw strips has a third surfaces facing to the paper feeding direction and a forth surface facing against the paper feeding direction, the third surfaces are arranged in parallel, and the depth of gaps between the bottoms and the tops of the forth surfaces is decreased along the paper feeding direction.
 9. The paper separation device according to claim 2, wherein the protrusions are a plurality of circular protrusions.
 10. The paper separation device according to claim 9, wherein the size of gaps between two adjacent circular protrusions is decreased along the paper feeding direction.
 11. The paper separation device according to claim 9, wherein the depth of gaps between two adjacent circular protrusions are increased along the paper feeding direction.
 12. A sheet feeding apparatus, comprising: an input tray, for placing a plurality of papers; a paper picking device, for performing a paper picking operation on the papers; and a paper separation device, comprising a paper separation surface contacting with the papers placed on the paper tray, for applying a paper separation force on each of the papers as fed in; wherein when the paper picking device performs the paper picking operation on each of the papers, the paper separation forces applied on the papers are decreased as their paper separation paths are increased.
 13. The sheet feeding apparatus according to claim 12, wherein the paper separation surface comprises a plurality of protrusions arranged along a paper feeding direction for providing the paper separation force.
 14. The sheet feeding apparatus according to claim 13, wherein the protrusions of a regular or an irregular shape have the same or different height.
 15. The sheet feeding apparatus according to claim 13, wherein the protrusions are a plurality of saw strips.
 16. The sheet feeding apparatus according to claim 15, wherein the size of saw gaps between two adjacent saw strips is decreased along the paper feeding direction.
 17. The sheet feeding apparatus according to claim 16, wherein each of the saw strips has a first surface facing to the paper feeding direction and a second surface facing against the paper feeding direction, the first surfaces are arranged in parallel, and the second surfaces have decreased inclined angles against a vertical line of the paper separation surface along the paper feeding direction.
 18. The sheet feeding apparatus according to claim 15, wherein the depth of gaps between two adjacent saws is increased along the paper feeding direction.
 19. The sheet feeding apparatus according to claim 18, wherein each of the saw strips has a third surface facing to the paper feeding direction and a forth surface facing against the paper feeding direction, the third surfaces are arranged in parallel, and the depth of gaps between the bottoms and the tops of the forth surfaces is decreased along the paper feeding direction.
 20. The sheet feeding apparatus according to claim 13, wherein the protrusions are a plurality of circular protrusions.
 21. The sheet feeding apparatus according to claim 20, wherein the size of gaps between two adjacent circular protrusions is decreased along the paper feeding direction.
 22. The sheet feeding apparatus according to claim 21, wherein the depth of gaps between two adjacent circular protrusions is increased along the paper feeding direction. 